I could not find anything about Motorized Bicycles or assisted Bicycles for Alabama. I could also not find what they consider a moped. Most DMV web site's will have something about Moped's, assisted bicycle's, or Motorized bicycle.

The only thing I could find was "Other Vehicle's" This includes scooter's and moped's.

Alabama Other Types of Motorcycles - AL Scooter & Moped Info - DMV.ORG

You might want to check with your local law inforcement, call, stop by, e-mail, they may be better off telling you then DMV.

I hope this was some help